CHICAGO: A week after five Americans were injured and a foreign contractor working for the US was killed during a rocket attack on a military base near Erbil International Airport in northern Iraq, Washington has yet to decide how to respond to the escalation of violence. In the meantime there have been two additional attacks on US-linked targets in country: at least four missiles hit Balad Air Base, north of Baghdad on Feb. 20, leaving one person wounded, and on Monday two rockets landed in the Green Zone near the US embassy in Baghdad. There were no reports of casualties in the latest attack.